Impact of coated and non-coated magnetic nanoparticles on oil-water separation in green surfactant-based emulsions

Abstract

This study investigates the efficacy of magnetite nanoparticles as a means of demulsifying surfactant-based emulsions, focusing on light and medium crude oil emulsions. The demulsification capabilities of bare, amine-coated, and oleic acid-coated magnetite nanoparticles were tested. Nanoparticle concentrations ranged from 0.25 % to 8 %. The emulsions used Alpha Olefin Sulfonate and two environmentally friendly surfactants, Coco Glucoside and Greenzyme with sodium and potassium formate as eco-friendly alternatives and sodium chloride as the standard brine. Magnetic demulsification efficacy is highly dependent on the interplay between the nanoparticle surface charge and surfactant, thereby affecting surfactant adsorption onto the particle surface. While gravimetric separation alone has partial effectiveness, the magnetic field enhances particle movement, promoting greater instability. The nanoparticles play a key role in adsorbing surfactant species from the interfacial region, thus facilitating demulsification. Notably, magnetic demulsification is more effective with environmentally friendly surfactants, achieving 100 % separation in most cases. Demulsification of emulsions containing synthetic surfactants is most successful with light crude oil emulsions, and in select cases, achieves 100 % separation with medium crude oil emulsions.